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How often is iodine supplementation recommended by U.S. midwives and obstetricians to their patients?

Clinical Thyroidology for the Public

Thyroid hormone is needed for normal brain development. Hypothyroidism in the mother during pregnancy can cause delayed brain development leading to decreased intelligence and mental retardation in the baby. Iodine is a micronutrient needed for thyroid hormone production as the thyroid hormones contain iodine. Iodine deficiency is an important cause of hypothyroidism in parts of the world. Iodine deficiency during pregnancy remains the most common cause of preventable mental retardation in the world. While severe iodine deficiency is not see in the US, recent surveys indicate that US pregnant women are considered mildly iodine deficient. Thus, several major medical societies recommend that women who are thinking of becoming pregnant, who are pregnant, or who are breastfeeding take a prenatal supplement containing 150 mcg of iodine daily. This study was a survey of U.S. midwives and obstetricians to assess their perceptions of iodine nutrition, as well as how often they recommend that their patients take an iodine supplement.

De Leo S et al. Iodine Supplementation in Women During Preconception, Pregnancy, and Lactation: Current Clinical Practice by U.S. Obstetricians and Midwives. Thyroid 2016 (ePub)

Through email, all midwife members of the American College of Nurse-Midwives and all obstetrician members of the American Medical Association were invited to participate in a web-based survey between June to December 2015. The email was sent out three times to obstetricians and twice to midwives, but each respondent could submit their answers only once. The survey first asked questions regarding the midwives’ and obstetricians’ demographic information, such as their age, region of the country their practice was located, what type of obstetrical practice they had, and years elapsed since they finished their medical training. Later questions included what they thought was the status of iodine nutrition among U.S. pregnant women, the potential health effects of iodine deficiency during pregnancy, usefulness of iodine supplementation for women of childbearing age and for pregnant women. Respondents were also asked how often they recommend iodine supplementation to their patients, as well as the quantity of iodine recommended daily for those that do.

Overall, there were very few respondents: only 199 midwives and 277 obstetricians answered the survey, corresponding to 3.6% and 1.2% of all U.S. midwives and obstetricians, respectively. From their answers, about one-third thought that U.S. pregnant women are iodine deficient. However, despite this, about 70% of midwives and obstetricians stated that they rarely recommend that their patients take an iodine supplement, whether in women planning a pregnancy, who are already pregnant, or are breastfeeding. Of those who do recommend iodine supplementation, only 45% would prescribe the recommended level of 150 mcg of iodine daily during pregnancy. Taken together, 75% of U.S. midwives and obstetricians who participated in this survey do not recommend or would recommend an inadequate amount of iodine during preconception, pregnancy, and lactation.


Iodine deficiency remains a major public health challenge. This is especially important among women of childbearing age in whom poor iodine status may result in adverse health outcomes for their babies, such as mental retardation and developmental delays. Many major medical societies have recently recommended that women who are thinking of becoming pregnant, who are currently pregnant, or who are breastfeeding take an iodine supplement containing 150 mcg of iodine a day. However, this study suggests that the majority of U.S. midwives and obstetricians do not make these recommendations currently to their patients. Increased education about this important topic is needed to improve the health outcomes of pregnant women and their developing children.

— Angela M. Leung, MD, MSc

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Iodine Deficiency: iodine-deficiency

Thyroid and Pregnancy: thyroid-disease-and-pregnancy


Iodine: An element found naturally in various foods that is important for making thyroid hormones and for normal thyroid function. Common foods high in iodine include iodized salt, dairy products, seafood and some breads. Iodine is also present as a micronutrient in some vitamins and supplements.

Hypothyroidism: a condition where the thyroid gland is underactive and doesn’t produce enough thyroid hormone. Treatment requires taking thyroid hormone pills.